Eibinger Manuel, Ganner Thomas, Plank Harald, Nidetzky Bernd
Institute of Biotechnology and Biochemical Engineering, Graz University of Technology, Petersgasse 10-12/1, 8010 Graz, Austria.
Institute for Electron Microscopy and Nanoanalysis, Graz University of Technology, Steyrergasse 17, 8010 Graz, Austria.
ACS Cent Sci. 2020 May 27;6(5):739-746. doi: 10.1021/acscentsci.0c00050. Epub 2020 May 6.
The cellulosome is a supramolecular multienzymatic protein complex that functions as a biological nanomachine of cellulosic biomass degradation. How the megadalton-size cellulosome adapts to a solid substrate is central to its mechanism of action and is also key for its efficient use in bioconversion applications. We report time-lapse visualization of crystalline cellulose degradation by individual cellulosomes from by atomic force microscopy. Upon binding to cellulose, the cellulosomes switch to elongated, even filamentous shapes and morph these dynamically at below 1 min time scale according to requirements of the substrate surface under attack. Compared with noncomplexed cellulases that peel off material while sliding along crystalline cellulose surfaces, the cellulosomes remain bound locally for minutes and remove the material lying underneath. The consequent roughening up of the surface leads to an efficient deconstruction of cellulose nanocrystals both from the ends and through fissions within. Distinct modes of cellulose nanocrystal deconstruction by nature's major cellulase systems are thus revealed.
纤维小体是一种超分子多酶蛋白复合体，作为纤维素生物质降解的生物纳米机器发挥作用。兆道尔顿大小的纤维小体如何适应固体底物是其作用机制的核心，也是其在生物转化应用中高效利用的关键。我们通过原子力显微镜报告了单个纤维小体对结晶纤维素降解的延时可视化。与纤维素结合后，纤维小体转变为细长的甚至丝状的形状，并在低于1分钟的时间尺度内根据受攻击底物表面的需求动态地改变这些形状。与在沿着结晶纤维素表面滑动时剥离物质的非复合纤维素酶相比，纤维小体在局部保持结合数分钟，并去除下面的物质。表面随之出现的粗糙化导致纤维素纳米晶体从末端以及通过内部裂变得到有效解构。由此揭示了自然界主要纤维素酶系统对纤维素纳米晶体解构的不同模式。
